This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Previous studies have shown that proper ion exchange and transport across the parietal cell membrane is essential for normal gastric acid secretion. For example, genetically engineered mice deficient for the Na+/H+ exchangers Nhe2 and Nhe4, the Cl-/HCO3 exchanger Ae2, and the K+ channel Kvlqt1 showed significant impairments in acid secretion. In addition, achlorhydric gastrin-deficient mice showed alterations in gastric expression of the water channel aquaporin-4 (Aqp4) and the chloride channel Clca3. The patterns of gastric expression of these genes during embryonic development or as mice age is unknown. Gastric acid secretion is thought to be initiated immediately before parturition;in addition, evidence suggests that there is an increase in gastric acid secretion as mice age. Understanding the expression patterns of Aqp4, Clca3, Nhe2, Nhe4, Ae2, Kir2.1, and Kvlqt1 both in development and in aging mice may yield clues as to the timing of initiation of acid secretion as well as the age-related increase in acid levels. The overall goal of this research is to analyze developmental and age-related expression of various channels and exchangers important for normal acid secretion, including Aqp4, Clca3, Nhe2, Nhe4, Ae2, Kir2.1, and Kvlqt1. The hypothesis of this study is that the gastric expression of these genes increases at later embryonic developmental stages and increases as adult mice age. Specific Aim 1 will focus on gene expression analysis and gastric immunolocalization of candidate molecules during embryonic development. Specific Aim 2 will analyze gene and protein expression patterns of these candidates in aging wild-type and gastrin-deficient mice. Determining the expression patterns of these genes in murine embryonic development as well as in aging mice will allow a more thorough understanding of mechanisms that that regulate the gastric acid secretory system. This research will have an impact on the field of gastrointestinal biology by further elucidating the developmental and age-related regulation of gastric acid secretion.